Advanced techniques of epitaxially growing semiconductor materials, for example, metal organic chemical vapour disposition (MOCVD), have resulted in layer thickness control to near-atomic values. This has led to the development of new active device structures such as multilayer configurations incorporating multi-quantum-wells and asymmetrical confinement layers. These developments have, in turn, resulted in the realization of surface or buried corrugations in Distributed Feedback (DFB) or Distributed Bragg Reflector (DBR) injection lasers. Precise control over the depth of etched corrugated waveguide gratings is, in fact, an important aspect in the processing of many optoelectronic devices. In DFB lasers, for example, grating depth is an important criterion in determining the magnitude of the coupling coefficient. The aforementioned asymmetric confinement layers are instituted to reduce the carrier transport limitation of a laser response to direct current modulation. In such a configuration the confinement layer, which can be of the order of 20 nm, must be corrugated to achieve single, longitudinal mode operation. Further, gain coupled lasers have periodic corrugations which extend into one or more quantum wells. Accurate positioning of such etched gratings is critical to device performance. Growth techniques which permit the formation of very thin devices necessitate accurate control of etching processes in order to properly locate the corrugation, grating, etc.